Electrical musical instrument



May 25, 119433.

. R. C. FISHER ELncTRIcL uusIcAL Ilus'rnuuEN'r Original Filed July '20,

4 Sheets-Sheet 1 ATTORNEY May 25, 1943. R. c. FISHER Re. 22,321

ELECTRICAL MUSICAL STRUMENT Original Filed Jly 20, 1932 4 Sheets-Sheet 2 'ATTORNEY May 25, 1943.- A R. c; FISHER RQ. 22,321 nLEcTnIcAL nmsIcAL Ins'muusn Original Filed July 20, 1932 4 Sheets-Sheet 3 Lum-nr (W) 'vl-Mnxv NVENTOR Kay/)10,716 Frs/fer,

' ATTORNEY May 25.11943.

R. c. FlsHgR ELEcTRIcAL- MUSICAL INSTRUMENT origingl Fnac; July 2o. 1932 4 Sheets-Sheet 4 mf( fw y .V e im ,www m A. mf n. n

Reissued May 2.5,l 1943 ELECTRICAL MUSICAL mSTRUNl-ENT Raymond C. Fisher, Tacoma, Wash.

Original No. 2,955,719, dated September 29, 1936, Serial No. 623,639, July 20, 1932. Application for reissue March 14, 1938, Serial No. 195,850

34 Claims.

This invention relates to thev art of producing musical tones by electrical means. It has application to musical instruments played manually or automatically by means of player rolls, or to both. Among manually played instruments, it has particular "application tothe keyboard type. It is, however, neither an organ nor a piano, but produces or originates its tones by means entirely distinct from those employed by either.

The objects of this invention are several. The first of these is to provide a musical instrument capable of producing, in certain `of its forms, tones of a timbre closely resembling that of the piano, organ,and/or common orchestral instru- -ments. It is capable of imitating not only sustainedtones, but can also, for example, imitate the rather sudden onset and gradual dying away of a piano tone. At the same time, and in the same instrument, it can, moreover, create new tonal effects such as cannot be produced by any mechanical or pneumatic means. Its possibilil. larly as compared with the pipe organ.

lieve that there is a need for such as instruties for the'development of the music of the l future are thus very great. It has been' the history of music thatl musical composition and technique have progressed largely according to,

and in response to, the invention of instruments for the performance oi music.

Another object oi the'invention is to provide an instrument which can modulate a radio transmitter or transmit music by wire, Without the intermediary, between instrument and ether, or instrument and wire, oi a microphone. The advantages in freedom from room reverberation, unwanted sounds produced in the room -where the microphone is located. improper balance between the various voices of an instrument due to unfavorable placing o'f the microphone relative to certain portions of the instrument, etc.. are scarcely to be overrated. 'I'hese diillculties arise particularly in rooms which have not been specially treated acoustically to make them suitable for broadcasting.

Another object*l is to provide an instrument which can, as has been said, be operated either manually or automatically.

A fourth object is to free the musician from the dimculties which arise when, as frequently occurs, his instrument gets out of tune. 1t

will appearlater that, in the present invention, so long as the speed oi the driving motor incorporated in it is held constant, which is not at all a diilicult matter, the instrument cannot possibly "get out o! tune". Also, the pitch relationship between any two tones which it is capable of producing must remain constant regardless of temperature, humidity, or age or fatigue of its parts, solong as they do not'actually break. In the piano, las is well known, the pitch tends to drop with age, due to the stretching or slipping of the strings. The organ likewise changes in pitch with every change in temperature, and

usually its various pipes do not all change by the same amount. Y

The invention has as a fifth object to make possible the building of an instrument which is simple, compact, low in ilrst cost and maintenance expense, and light in Weight, particu- I bement, particularly for installation in homes, hotels, cafes, undertaking establishments, and the like, and more especially in those already constructed wherein no provision has been made for an instrument having the bulk of a pipe organ.

The pipe organ has been called'a one-man orchestra. Thisis inaccurate insofar as the organfails, as it generally does, in imitating accurately the tonal peculiarities of orchestral instruments: Nor is it an easy task to so construct the organ that it can accurately imitate them. The conditions under which the tone is produced being different in the original instrument and in the organ, and the re ons for the diilerent tonal qualities of diierent types of organ pipes being imperfectly understood, the process of designing an organ pipe to have a certain desired tone quality is of necessity largely an experimental and empirical, one. On the other hand, the instrument constructed according to this invention is capable of synthesizing any of a vcan be constructed more cheaply than the many instruments it displaces. It is possible'tojconnectmany keyboards with one such instrument, thus enabling a number of Y musicians to simultaneously play on the same in- `strument. Since the volume of sound associated ywith any one keyboard can be varied through very wide limits, it is possible, foriexample, for one musician, atgone keyboard, to take the place of al1 the tlutists and ot all oftheir flutes, in a largo symphony orchestra. In addition. and simultaneously.- other musicians `at other keyboards would be taking the place of other groups of inl strumentsin the orchestra.

It is quite generally conceded thata melody which can be played, lfor. example, on'a flute, an

oboe, 'or a saxophone, can be played more easily on a keyboard instrument, and that less skill is -required for its execution on the latter.4 The present invention thus makes a comparatively unskilled musician, in eiIect, a ilutist, an oboe player and a saxophone player, all three. Likewise a pianist or an organist may be able to nearly perfectly imitate `the ilute, almost without practice in such imitation.

'I'he production, for laboratory and other uses,

of alternating electric currents and voltages oi accurately controllable frequency and'wave form,

is another purpose of this invention. It is well tion to certain novel features of construction, op,

feeble voltages generated by variable-condensers.

With the above and other objects and advantages in view, this invention has particular relasperation, arrangement of parts and methods of known to researchers in the electrical ileld that this has hitherto been a task of considerable importance, but one diilicult or impossible to Y achieve, according to the degree of accuracy of wave form demanded. I

It is well known (see Websters Unabridged` Dictionary, under `the word ione, in sense 2a), that sustained musical tones are characterized by their pitch. timbre, and intensity, and that their timbre is determined by the proportions of so-called partiels which they contain. -Hence a sustained musical tone of any desired `timbre or quality can be synthesized by simultaneously producing several component sound waves of the Aproper relative pitches and intensities'.

In the present instrument, periodic variations of electric current or voltage are produced and, with or without intermediate electric circuits, are caused to operate a telephone receiver, usually a loudspeaking receiver, and often moretthan one.

It ls'by no means necessary that Vthe loudspeaker which is operated Vbe connected by wires with the part of the apparatus which originates the alternatingcurrents' and voltages. The latter could, for example, be used -tdmodulate a radio telephone transmitter, in which case the loudspeaker might be.a part of a radio receiver.

. Nevertheless. the primary purpose. of the invention is the production of musical tones; 4that is, of tones characterized by definite pitch and timbren' f.

In brief, my invention contemplates the production oi' alternating electric currents and electromotive forces of a greater or less degree of complexity, which are subsequently amplified and caused to operate a loudspeaker or telephone receiver, which terms, as I use them, throughout this application, include the electrostatic loudspeaker or receiver, the electrodynamic loudspeaker, the magnetic loudspeaker. the piezoelectric loudspeaker, and, in fact, all devices Vfor converting or translating varying electric currents or voltages into sound waves. In addition, the invention includes means for controlling `the volumes, the

use, examples of which will be given in this speciiicatlon and illustrated in the accompanying drawings, wherein:

Fig. 1 illustrates, diagrammatically, one preferred simple form oi' the invention;

Fig. 2 represents a simplified diagram of the circuit oi' Fig. 1, includingonly those parts of Fig. i which .are operative when certainkey and stop contacts are closed and certain other contacts are Fig. 3 shows a still further simpliiled schematic circuit, electrically equivalent to that of Fig. l:

Fig.v 4 shows a schematic circuit of a simpleV form of the invention, in which are employed a high-frequency source and a detector;

' Fig. 5 illustrates schematically a part of the invention, diil'erent in certain respects from that in Fig. 1i

Figs. 6, 6n and 6 show schematically, means for' controlling the rate at which the volume of sound increases to a maximum and` again dies away,

`after a key of the instrument is pressed;.

Figs. 7 and 8 illustrate still other ways of accomplishing roughly the same ends as does the circuit of Fig. 6:

Fig. 9 shows a type of volume control having certain advantages:

pitches, and the timbres of the various compo- Y nents comprising the sound. f

VI am well. aware that United States Letters Patent' for means designed for accomplishing generallysimilar ends have already ,been granted f to others. I believe. however, that my invention has the advantages of a degree of simplicity, .compactness and inexpensivencss oi construction greater than are by any of these other inventions whose musical possibilities are comparable. The simplicity of the variable condenser as a source of alternating electromotive vi'orce y'is'mainlxr lPOnsible i'or this. So i'ar as I am aware, no one has ever before employed variable condensers for originating musical tones of a particuiar desired waveform, or. as-may be better i stated, of any prescribed waveform, (I do not mean to include in thisstatement the reproduction oi' musical tones) :or oi' the electric currents 4which are their electric Electric cur- Vrents'fax'id voltages are quite readily. cheaply and faithfully amplified by vacuum tube amplifiers of modern design, a fact which makes possible thel utilization for musical purposes oi'` the rather Fig. 10 illustratesin plan mechanical details showing the tone bands used when electrostatic means are used for the production of musical tones, together with the mechanism which drives them, the prime mover, and the speed-control apparatus.

Fig. 10* is a side elevation of the same parts; Figs. 11 and 11* show two forms of stator plates; Fig; 11b shows a variable condenser for producing irregular wave shapes;

Fig. 12 shows a condenser ofa modified form ill-v iustrated diagrammatically at I in Fig. 6".

Like. numerals designate the same parts throughout the speciiication. s f

Referring to the circuitshown in Fig. 3, 2| is a source of unvarying electromotive force, such as a'dryl battery, 22 is a resistance, and 23 is an electrostatic condenser. If the capacitance or the condenser is caused to vary, the quantity of electricity stored in it will vary. and there will be a variation oi' negative reactance and current in the circuit and -a voltage drop in the resistance.--

It is on a similar principle that the usual condenser microphone operates. The voltagedrop in resistance 22 resulting from the-current in itz, is applied to the input terminals oi an amplier 24. The .electrical output energy of the ampliiler is made to operate a telephonereceiver or loudspeaker 25."

I'he circuit or network `iised in one form of the invention forming the subject oi' this application is illustrated in Fig. 1. Its operation will be explained by showing 'that it is electrically equivalent to the circuit oi Fis. 3. Notwithstanding this electrical'equivalence, which* applies to the two diagrammatic circuits only, the invention forming the subject of this` application diners from the condenser microphone and its associated circuits in several important respects. .In the ilrst place the capacitancee of this invention are varied mechanically as, for example, by rotation by i an electric motor, instead of acoustically, as in the microphone. In the secondplace. if I am to cult to understand.

have acceptable musical effects or practical control over wave-form or frequency, I must provide Y and a fth interval above middle C), the second means for selecting certain condensers, or combinations, as wanted. This may, as has already been said, be accomplished manually, or automatically from a music roll or the like. In the third place, it is the purpose of the condenser microphone to reproduce sound, whereas the present invention produces or originates sound. The microphone setsup electric currents and voltages which are replicas of the sound waves impinglng upon it, Whereas the type of .variation of the currents and voltages inthe present invention lare not replicas of sounds produced simultaneously by sound sources external to the invention. f

By waveform, I mean to refer to the curve, or function, expressing a capacitance, a current, a voltage, or the likeas a function of time. By a prescribed'waveform, I mean a waveform after the above definition which has been determined upon in advance as a "pattern or model" for the device to follow in its operation. In accordance with the Standardization Rules of the American Institute of Electrical Engineers, the wave? form, or wave shape, is independent of the frequency and of the scale to which it is plotted. See, in this connection, the Standard Handbook for Electrical Engineers, section 24, page 1818, fourth edition, third impression, published by McGraw-Hill Book Company, Inc., New York, N. Y.. By originating a waveform, I mean that the waveform has its inception in the apparatus, not externally in an automatically-made recording of a previously executed sound, such as a phonograph record, and not from sound waves in free space arriving from outside the apparatus as in the condenser microphone above discussed. In other words. my invention operates actively to originate the waveform, not passively to reproduce a waveform having its origin elsewhere. Y

In the invention as arranged for use in a musical instrument, the desired tones are probably most readily turned on by means'of aI keyboard similar to that of a piano, and the timbre conltrolled by means of stops like thoseA ofY a pipe L nected in the circuit. It will be noted that conharmonic overtone of the fundamental D, and

the second harmonic overtone of the fundamen tal E. A. preferred mechanical form of these variable condensers will be described hereinafter.

' If stop Il be closed through contacts I3, Il and i5, xed condensers i3', Il' and I 5 will be condenser I3' is connected to the second-harmonic condensel's I, 6 and 8. Hence its electrostatic capacitance determines the magnitude of current in the circuit of second-harmonic frequency. Likewise condenser it' determinesthe magnitude of first-harmonic current, and i5' determines that of the fundamental current. Stop 2li, if closed through contacts I 6, i1 and IB, would connect fixed condensers |6211' and IB', which may be respectively of different capacltances from 4i3', Il' and i5' and may laccordingly give partials'havlng different magnitudes Arelative to one another. Thus a different timbre may result from closing stop zu from that 'which follows the closing of I9. Obviously from Ohms law, the alternating current impedances of each of the parts I3 toV Il must-in general be materially greater than the intern-al impedances of the circuit meshes which they form in conjunction with any one of their associated variable condensers as a organ. Whereas the condenser microphone conf sists of a single condenser in most cases, there are' in certain forms of the present instrument a number of variable condensers; in some forms there is one for each fundamental tone which I wish the instrument to be capable of producing, and one for each of the overtones.

In Eg. 1 is schematically illustrated one form which this invention might assume. It is obviously necessary to be able to control the rela? tive intensity of the various partials of a tone, as mentioned above, if I am to select any timbre at will. Since Fig. 1 is illustrative only, it shows an instrumentwiththreenoteathreepartialsto -eachnote (fundamental and two harmonics),

and two stops.l A schematic "view including additional notesvand stops will show additionally l; appropriate duplications o f these and will make source, and pant 22 as a sink, if vthey are to limit the current through themselves sufficiently to perform their task of determining the timbre.

It should be mentioned that condensers i3',

' u', l5', le', I1' and ls' should be slightly leaky,

yand condensers l', 2, l, 4, 5,6, l, 8 and 9 should be well insulated. Otherwise a maximum polarizing or exciting voltage from the battery 2i will not exist across 'condensers I to 9. and the variation in charge due to their capacitance variations will be feeble or lacking.

Numerals Ill, Ii', and i2' indicate the key contacts of the instrument, and determine which note (with proper tone quality or timbre as selected by closing a suitable stop) will be sounded.

As a result of the variation of the capacitances in the circuit, alternating currents flow in the .resistance or other coupling -elemen-t 22. potential drops setl up therein are amplified by The the amplifier 24 '(usually a vacuum" tube ampliiler) and the resultant amplifier output is made to operate the loudspeaker or telephone receiv- To f-urther explain the operation and action of vthe instrument. 'let me assume that key Il and stop I9 are closed. This brings into play variable condensers I, l and l, and also fixed condensers il', I Il' and Il'. electrostatic capacitances between other key and stop contacts and also between wires, etc., in Ithe apparatus are negligible,condensers I., 2, J, 1, 8, 9, il', I1' and Il' are not operative.l Hencethe partorfthecicuit'vrhcliis'lisednlaybel'edrawn4 as shown in Fig. 2.' This circuit can be further 1 simplified to. that of Fig. 3, if the observation is made that condensers I, l, l,'ll', I4' and Il' are electrically equivalent' to a single condenser 28 (Fig. 3) .whose capacitance varies ina compli- Vcate'dmanner. If obherkeysorstops'hadbeen operated, -I should have had to represent'the operative condensers by a single condenser whose capacitance varies in a different manner. VIt is clear, then, that Pig. 3 does not 'show a circuit diagram of the musical instrument, but only 'a amat electrically' equivalen-.rm we mom 1- plicated one of the instrument Provided the stray only.

In addition, Figs. 2 and 3 show one manner notall of the same resistance..

special conditions. and its purpose is illustrative in which the alternating currents produced by the action of :the variable condensers are made to produce sound. "I'hese alternating currents now" thrcaigh coupling resistance 22, just as in Fig. 1,'

and produce across it potential drops' having the same frequencies as have the currents. Across resistance 22 are connected the input terminals of a vacuum tube ampliiier. To the output terresult.

tial resident upon condensers I, 42 and I as a 'Ihat` on I will be dependent upon the electromotive force of source 2| and also upon the relative resistances -of the resistors Il and 5I. In a like manner, that on 2 will be dependent upon the relative resistances of the resistors Il and u, and that on 2 will be dependent upon the relative resistances of l2 and 4l. It is seen that these minalsofv this amplifier is connected -a loudspeaker or telephone receiver,` whose function it is to convert the amplified electrical energy into sound waves.

One practicable means of controlling the volume of sound emitted by the loudspeaker is to make resistance 22 in the f orm oli a potentiometer;

pair: of resistors are voltage dividers whose purpose it is to select a certain part of the total electromotive force of source 2|.` When the capacitances of condensers I, 2 and I Vare made to vary ,cyclically, the variable components oi' the charges on them are proportional to the direct potential differences on them, and so the relative strength of the three partials of the composite tone is under control.

The portion of resistance 22 which is shunted by l the ampliiler input terminals is variable and thus. a greater or lesser fraction of the total IR drop in element 22 may be ampliiied and introduced tothe sound translating device. G

vAnother form of the invention is illustrated by Fig. 1 if I let symbols I3' to I2' inclusive represent iixed or manually variable resistors instead of condensers. Resistors can-be made to regulate the relative magnitude of the partiels of a tone, Just as condensers can.

In Fig. 4 Ais illustrated still another form which the invention may assume: Like numbers represent the same components as they do in Fig. l. Inaddition, Zlis a source of high-frequency or supersonic current.. 'I'his diagram' shows an insti'un'ientvwithout stops and ivith but one Vkey and one variable condenser.

stops is analogouaor maybe analogous, tothat of Fig. 1, the c hieidiiference between the two iigures being that one uses abattery andthe The method of con- .nectingother keys and variable condensers and,

, -term a quasi-linear circuit."

radio receivers. The low-frequency output of.

source canbe use d in conjunction with a con- -de'nser or` condensers variable by mechanical means for theA vproduction of Amusical sounds. Fig. 4 illustrates only one such way.

The relative intensities oi' fundamental and overtones can becontrolled by controlling the *amount of .direct electromotive force from thel battery which is applied to the variousvariable Y condensers. Fig. 5 illustrates schematically one possible circuitfor accomplishing this.` In this figure. most of the numerals representthe same things as in preceding ilures. l

' In general, the resistors-Just mentioned are thatv key contacts I2", ll"`an|.'ll II'" are all closed by depressingl the key associated with them, and

-.necessary under certain conditions to insure a quasi-linear circuit with resultant freedon, or comparative freedom, from unwanted frequencies in the circuit. These frequencies can be mathematically shownto exist to an objectionable degree in the absence of condenser 5|, especially when the resistance of resistor 22 is very migh.

Thereduction of the resistance gives what I The increase of capacitance -giveswhat I term a distortionless circuit, which is a, particular-kund oi' quasilinear circuit." i

On the keys or switches I0, II and I2, Fig. 5, I show upper contacts. 'I'hese are desirable at times for the purpose of short-circuiting the variable c ondensers with which they Aare associated, `so that these condensers cannot produce in the circuit, in cooperation with stray' capaci'- tances or leakage, alternating currents of the frequency with which they vary, at times when such frequencies aie not wanted. This shortcircuit is by a path including a Vparticular upper contact, and the conductor lB4 at the left-hand side of the ilgure. f Y

Fig. 5 does not show the ampliiler and loudspeaker, since these may be connected to resistor, 22 in the same manner as. in preceding gures.

Ihave Vfound by experiment that in certain cases the onset of a tone, when no special means are employed to avoid this, may be unpleasantly desirable to provide means -ior eil'ecting a less Leimeassuine` abrupt onset and a less abrupt decay of the tone aswell.

One such means is illustrated in Fig. 6. l Instead of closing the circuit by means of a Single pair of contacts like those of; previous gures. a

number o! contacts II' are provided. which are the right-hand end of 'the key rises. resistanceis gradually cut out of the circuit-,and the tone starts gradually. also, it ceases gradually when thatstop II is also\closedwith stop 2l open.

There 'will bea certain diiiercnce oi.' direct potenan alternative. method, naviiig 'the advantage nitudes of elements 52 and 3.

` able.

here also.

In Fig. 6b, I illustrate another means for securing a gradual onset and dying out of a tone of any-given pitch. This particular form is sometimes desirable in order to imitate other musical instruments, such as the piano. If, in series with any keycontact i and the source of direct E. M. F. 2i, there be connected a resistor 52, and

vif a condenser 53` be placed in the circuit as shown, then when contact lli' is closed, the direct potential drop across variable condenser I will not rise instantaneously, but at a controlthe note -becomes loud. Its loudness is dependent upon the capacitance between members G5 Iand 1l, which is in turn dependent upon how vhard ablow member B5 receives from the key lever and its consequent excursion upward.

The valves on the dashpot permits the condenser plate to move upward with freedom, because it is designed to open for the upward motion of the piston. As the condenser plate falls again, however, valve 10 closes. If the pedalcontrolled valve 61 or the key-controlled valve |51EL is closed, the plate very gradually returns to its lowest position, and just before it reaches it,

' contact B9 reopens. All is again inlreadiness for lable rate, dependent upon the electrical magu Thus an unpleasantly sharp onset of tone may -be obvia'ted or a gradual swelling in loudness may be effected, which has great musical possibilities. During the release of the key, contact ID" is preferably made before i0' is broken. When contact iii is closed and Iii open. then, provided the sostenuto switch 55 is closed, condenser 53 discharges gradually through contact lll", switch Since the rate of dying away is dependent upon the' resistance of 54 and 55, and resistor 55.

the capacitance of 53, it can be controlled by varying the resistor 5I. The circuit elements 54 and 55 may be operated by a stop or pedal which also bears contacts for other switches controlling condensers similar to 53, but connected to others of the variable condensersin the instrument. When resistor 54 has a. very low resistance, the tone ceases immediately upon releasing the key, :just asithe tone of the piano does when the sustaining pedal ,is not depressed.

Wi-th open, 53 will discharge only via leakage paths, and hence the tone may be sustained for a very long time, until the pedal is released.

As compared with the present invention, the

plano h'as the disadvantage that its tones die away slowly, even when the keys are held down. This is, of necessity, the case in any percussion tO-it.

In Fig. 7, I illustrate a type of key and action which accomplishes what the circuit of Fig. 6

- does, and more besides.

WhenI key lever 62 is operated, the upright piece 63 on its right-hand end is raised. It

strikes condenser plate 65 and raises it, together ward due to its inertia to a position alongside ystatlonry condenser plate 1I. Both are shown in side elevation, and the clearance between the two, when plate 65 is raised, is a few hundredths of an inchl only. This condenser composed of parts 05 and 1I, with airdielectric, shunts the audio frequency currents around resistor 66, and

However, plate 65 continues to swing upinstrument unless some sostenuto device be added ting 65 to fall and contact 69 playing the same note once more. The descent of 65 is slow, unless both valves 61 and 61 are open. The rate of descent is controllable by opening valve 51 more or less widely by suitably operating pedal 53.

In Fig. 8, I illustrate another type `of mechanism which accomplishes the same thing as that of Fig. '7, but has certain advantages over it. .All similarly-numbered components are like those of Fig. 7, and perform identical functions. Instead of a dashpot,'however, this device utilizes a rotating shaft H. The speed at which pulley 12, with its ratchet 13, is rotated by prime mover 32 is dependent upon the tightness of the belt 15 between them,'which is under the control of foot pedal 68. When the pedal is not pressed, the idler pulley 12 keeps the belt taut, and pulley 12 .rotates with its maximum speed, When the key lever B2 rises it strokesconde'nser plate '65 and causes it to rise to a heightsdependent upon the force of the blow which it. imparts to it, just as in Fig. 7. In addition, it raises stop 13b into contact with ratchet wheel-13e. The friction between parts 1?a and 1lib is greater than that between 13a and the shaft with which it has just been rotating.- Its rotation is stopped, then, as long as the key is depressed, even though the shaft may go on rotating.l

When condenser plate 65 has :risen to the top of its arc 'of motion, the pawl 13 which it carries engages ratchet wheel 13, and it remains in that position until the key is again released, wheel 13a resumes its rotation, and plate B5 falls, as fast as the rapid rotation of the shaft will permit. The capacitance between 65 and 1I becomes less and less during the fall, decreasing the volume of the tone rapidly but not instantaneously, and nally contact E! breaks when plate 65 has come again to nearly its lowest position.

If the shaft with which ratchet 13" rotates is made to rotate slowly or to stop altogether, reason of pedal 68 being depressed, the tone will be prolonged after key lever 62 has been released. The length of .time the tone is prolonged depends upon the rate of rotation of the shaft, which can be controlled through wide limits by depressing When the pedal BB is released, the rapid rotation almost' immediately, lthus permitto break.

It is evident .that pedal E8 performs for the present invention just what the loud pedal does for the piano. It serves to maintain or prolong the tone after the key has been released, for a shorter or longer interval. In the present case, the pedal can prolong the tone ideiinitely, whereas 'in the piano, the -tone can persist only durlngfthe intervals when the strings are able to continue their vibration; However, it is unnecessary to prolong the tone indenitely if one chooses not to, for condenser plate 65 may be ratchet 'an audio ampller.

made to return at any desired rate to its position .of rest, according to how far pedal is rdepressed. If -the direction of rotation of the ratchets be reversed, atone may be `made to increasein volume after having been sounded, thusl producing a dynamic effect new to the art of music, and of great value to the composer and performer.

It is to be understood that an instrument having a/plurality of keys like 82 will also have a plurality of condenser plates. contacts vlike 69,

and ratchet mechanisms like 13. There will be one common shaft for the entire keyboard; one pulley like 12, and also one idler pulley like 12.

It has been found by experiment that even trained musicians cannot distinguish between the tones of certain musical instruments in case they cannothear the onset or end of the tone.

, It is seen, therefore. that the onset -and ending are characteristic of an instrument, and means for varying these, particularly the former, are desirable if a wide variety of musical eifects, both volume of tones in the neighborhood of 3,000 cycles more rapidlyas the resistance of coil Il is decreased, than it decreases the volume of tonesof substantially lower or higher frequency.'

imitative and new, are to be attained. It has been further discovered that, if the higher harmoncs of a tone attain their f ull amplitude appreciably before the fundamental and lower harmonies, the effect is that o f an "explosive onset; on the other hand, if the higher harmonics are later than the lower ones, the onsetis apparently a smooth and gradual one. L A convenient way of accomplishing. this is t Y mount the lower contacts of switches Ill", Il',

I2', Fig. 5, on a table or tables I l", which can be slightly tilted by means of a stop il". Since this is, practically speaking, a part of the switch, it has been given the same number Il, as' has the switch in Fig. 5. No tables or stops are shown at switches i0' and I2', since these might be identical with the table and stop Iln and Il, and in any case they would be of .similar construction.

If stop IIb is raised, the lower contact of switch |I', will be made rstwhen keyl Il is pressed, other contacts will follow sequentially.' and contact li'" will be made last. z Assuming -that the variable condenser 4 is producing'the fundamental tone and S the second harmonic, the onset of tone would be a comparatively gradual one. On the other hand, ii' stop I Ih were pressed down, the part AI l' would first make contact, and the onset would be more sudden.

In'Fig. 9, I illustrate another type` of volume control which I have found valuable. '66 represents -the plate of one of the vacu.um.ltubes of 51 represents the grid of the next succeeding tube. I8 is an audio-frequency transformer. The primary and secondary windings of the transformer are connected 1 respectively to 'the plate and grid, 'I8 and l1.

The other terminals of the transformer may return to the plate voltage Supply and to the grid bias supply in any one of several different manners, as is'well known to those skilled tn the ap- Plication of vacuumtubes for amplifying purposes. l l Y Across the primary winding of transformer Il, as shown;- ls r shunted a branch circuit consisting of a resistance 59, inductance II and condenser BI fin series.' Thenv'alues of resistance', capacitancefand inductance are so chosen that the 'branch .circuit resonates at about 3,000 cycles'.-

Resista'nce I9' is variable and its manipulation regulates the volume of bone from the telpphone receiver 'or ,other-sound emitterconnected to, the Vampliiier output. Such a volumel control as. this has .the proper-ity thatiti decreases The advantage of this is explained below. lThe frequency selective volume control shown in Fig. 9 may be used either with or without other means of volume control.

It is evident that such a volume control would work inthe same manner if connected similarly -to an amplifier having resistance or other type of coupling between succsive amplifyingaudioi'ls. the circuit than in the amplifier as, for example, in shunt |to the loudspeaker. ,It is to be understood that my invention comprises 4all such 1o'l cations for. the control and that it may be used either with or without other means'of volume control, its connection to the interstage transformer" being illustrative only. Its essential fea-r tures are that it is a shunt consisting of resistance, inductance andu capacitance in series, that it is placed somewhere lin the circuit between the source of alternating E. M. F. and the translating device or other output mechanism. and that it Iattenuates certain tones' more lmarkedly relative to others for low volumes of output than it does for high volumes, said tones discriminated against atthe low volumes being in that range whereto the human ear is moet sensitive.

Oli-Dese 230. in- Fig.\109 of "Speech and Hear-l 4 lng", 'by Harvey Fletcher, 1929 edition, there is illustrated a chart showing the'contour lines of equal loudness, as judged by ear, for pure tones. The meaning of the chart is explained in the context. 'Ihese contour lines show Ithat the average Vhuman ear has a maximum sensitivity for Vsounds in the neighborhoodof 3,000 cycles, and

:that as the energy content of a pure tone decreases .the -apparentloudness also decl-cases;` However, it is evident from the greater curvature of the lower graphs in the chart that .the appar-` ent loudne'ss decreases less rapidly foltones of about 3,000 cycles than for higher frequencies.

The type of volume control illustrated lnrlggs f 4 is capable, if properly constructed, of quite sat-y isfactorily compensating for this fact, inasmuch` 'as it cuts down fthe intensity 'of the 3,000 cycle output of theV 'amplier more rapidly than that of other frequencies. Thus the important resuitl follows, 'that .une apparent loud-ness of all* pitches of tone remains about constant, whether the instrument is emitting a loud or soft tone.-

'Ihere is the added fact that low-.pitched tones mask those of higher pitch. and'that this masking veileet is' more serious at high volume than at low volume. This also is discussed in the textV above mentioned. This masking -eil'ect is another reason for the desirability of -theabovedescribed frequency-selective volume control.

Itv would not be out of place here to include aword regarding whatI consider to be the most loudness.f Aninstrument designed according toi this assumption should be free' from Aobjection desirable form of curve relating the fundamental pitch of a tone emitted. and the apparent loudness. to the average human ear.,` of that tone. It would appear that all tones, whatever their pitch, should produceto the ear-substantially the same able masking lci certain tones by other-tones` Y .and should moreover exhibit a'pleasing' balance between bass and treble. Inv thev parlance of organ-builders. such an Vimtrmnent wouldbe Q f dennition properly ."vo'iced Or it might be connected elsewhere in 1 Vtones of lower orf4 of the amplifier.

oi proper voicing Iapplies only to tones under the 1control of a given keyboard. If there is more than one keyboard, it may be desirable to play the tones on one of these at a higher volume than the 'tones orfanother, so that, for examplathe melody can be made to stand out.

It is not always the case that a given amplifier and loudspeaker give tones of uniform apparent lou-dness, irrespective of pitch, for a given electromotive force applied to the input terminals For this reason, it may be desirable to so design the amplifier or speaker so that this loudness is apparently uniform. Another means for accomplishing the same end' is to so design that portion of the device which produces :the alternating E. M. F. applied to the amplifier that the apparent loudness is independent of pitch of fundamental tone. One way in which this may be accomplished is to regulate the dimensions of the several variable condensers in the input circuit of Fig. l. It is obvious that, the smaller )the change in capacitance as a function of time, the less will be the alternating electr-omotive force which it produces. Another method is to increase the minimum and maximum values of capacitance of a given condenser, maintaining the ydifference between these two values constant.` I am referring, of course, to the minimum and maximum values which are assumed by the capacitance cf the variable condenser -as 'itvaries periodisoidal law.

cally. It can be shown that, under proper conditions, this will serve to decrease the lalternating electromotive force. Still other methods are the insertion of alterna-ting current impedance in series with the variable condensen, so'that there will be an A. C. drop or loss of E. M. F. therein, and the lowering of the direct or highfrequency voltage impressed across the condenser in question. In the latter case, the alternating electromotlve force which the condenser is `able to impress on the ampller input terminals is lowered in the same proportion 'as the supply voltage is lowered, and becomes zero when this voltage is zero.

While Ithe foregoing discussion has been chiey conilned to the use of the invention as a musical instrumentor a part of one, it has been shown that, in order to produce musical tones, it is first necessary to produce alternating electric currents of controllable audio frequency and waveform.

lObviously., alternating currents. either with or without amplication, can be used for purposes other than the production of musical tones.` The use of alternating curren-ts of-controllable frequency and waveform inelectrical laboratories is one such other purpose. It has been considered unnecessary to show special diagrams of the invention in uses other than the production of musical tones, since these diagrams might be identical with those already exhibited. In general, an

- alternating current source for other purposes than the production of `musical tones would be simpler than the mus-ical instrument, for quite frequently the device need produce but one frequency at a time rather than a plurality, as is the case in most' musical instruments constructed after this invention. Moreover, oftener than not,

other uses, numerals lil to IB in Fig. I would represent switch contacts instead of key contacts and stop contacts. l

Reference has been made in the foregoing to variable condensers which generate the alternating voltages and currents as desired. These have been indicated to be of such form that each by itself generates a sinusoidal component of electromotive force or current.A In this case, each condenser would be of such construction that its capacitance'varies substantially according to a sinu- The functions of several condensers can, under certain conditions in practice, be economically combined into one condenser. In such case, the capacitance of a single 'condenser would vary cyclically, it is true, but not necessarily according to a simple sine law. My invention has application also to such more complicated laws of Variation of capacitance'. If condensers which are like that of Figure 11b, to be explained later, and which have irregular non-sinusoidal edges, are used in the circuit of Figurel or Figure 5, the result will of course be that non-sinusoidal currents will be combined in the circuit by the selectors. All condensers of a group, as I, 2, and 3, may produce the same fundamental frequency but each may produce a different waveform.

` Many variants are possible in the construction and electrical connections to the plurality of variable condensers. Without limiting my invention thereto, I illustrate in Figs. 10 and l0 a preferred mechanical form and arrangement of parts. Only a portion of the entire device is shown, since other parts will be for the purpose 'of producing other overtones and fundamental tones of other pitches. There is no real need of showing the various parts in extreme detail` and in their entirety, and to exact scale. The details may differ through rather f wide limits without rendering the device inoperasame shaft. `metallic band 30.

driving. the bands is similar to that of driving the photographic film in a motion picture projector.

Each band carries on that one of its two surfaces Which does not contact with its sprocket. a number of uniformly spaced lmetallic projections 3|, which I term scanning electrodes. 'Ihese extend across the bands and project slightly above their surfaces. Each band travels for a certain l distance beneath a stationary insulating member 3l. It is to be noted that .the solid insulating material is so disposed that it is substantially free from shifting electrostatic flux. The band is constrained to travel in a denite path, without whipping, weaving, etc. Attached to the insulating member 34 there are a number of plane metallic plates or electrodes 33, which are acthe provision of special means for regulating the type of onset and dying away of a current will be unnecessary for other lthan musical purposes.

These differences in detail (thoughnot in'principle) will be apparent to skilled lelectrical research workers. It Will suflice to point out that,

in one form of the invention as applied to these Two different forms of such stator plates are.

cordingly insulated from one another.. These I term stator plates. `Insulating plate 34 is repre-'I sented as broken away, so as to reveal more of the The statorbands 3U 'with 4their electrodes. plates have each one straight edge'll* and one edge 33h whose form is a chosen curve or Wave.

shown in Figs. 11' and 11B. lIt' is to be understood that other plates, shaped accordingto other s sui been invented-by others, and it is not my purposeto apply for a patent on any prime mover orspeed governor, but only to seekto patent their applipatterns, may be used; each is formed so as to produce a different` frequency of variation ofv capacitance. The plates appear edgewise in Fig. 10, and `their curved edges are shaded in the drawings.

The capacitance is made to vary as follows. As one 4of the electrodes moves along under the stator plates, it travels at a uniform rate of speed at a fixed distance from them, perhaps one onehundredthf an inch, but does not touch them. The width or dimension of an electrode, measured in the direction of the length of the band, is never greater than one-half of one `cycle ofthe curve cut into the edgeof anyofthe stator plates whichit passes. It is thus apparent that the electrostatic capacitance between the electrode.

and a given stator plate varies as the former passes along near the latter.4 For example, when the center line of the electrode is opposite the widestpart of a stator plate like that in Fig. 1l, there is a mainmum capacitance between the two; when opposite the narrowest part, there is a minimum of capacitance. Ii' one edge of the stator plate is in the form of asinusoidal curve and the other edge-is straight, and the distance between electrode and plate remains constant as the former moves along at a uniform rate of speed, then the capacitance varies with time in a simple `harmonic fashion. The length of each plate, and the spacing of electrodes is such that,

, just as one electrode is leaving the plate at one enl, the next is approaching it at 'the other; in other words, the electrodes are spaced on ceni ters whose distance apart is` equal to the length band is mentioned as frequently unavoidable. n

The electrode, in passing "a plate like that shown in Fig. 11, will generate one complete sinusoidal wave -of capacitance variation; in passing a plate like that in Fig. i1", it will generate two complete cycles roi' doublethe frequency generated with the plate shown inFig. 1l. l

I have found that, by using twenty-four bands, 523 different frequencies can be generated, which represent all fundamental 'tones ofthe chromatic scale or system of temperament. However, in order to produce all of the tones of anV eventempered musical scale, it is necessary that the diameters of the several. sprockets should in general bear irrational ratios to one another.

' In such a case, it can be shown that there will scale, together with the first fifteen harmonics f of each, from C of 32 cycles (scientific pitch) to C of 8192 cycles, except that harmonic frequencies above 8550 cycles are omitted as unnecessary to .the production of successful musical effects. The entire system of sprocketabands, and stator plates may be housed in by` five feet in dimensions.

vIn'order that the condenser capacitances maybe .continuously varied, the sprockets are all mounted on and rotatedby a single shaft, and driven, or actuated,` by a single electric motor or other prime mover 32. The speed of this motor `may be regulated to the requisite degree of ne-l` curacy by a governor I5, which may `beof any ev type. Suitable governors have' already cationvt the invention described in this specia box roughly one foot y' all of the otherv condensers.

necessarily beat least one space between adjacent electrodes on most of the belts or bands, which is abnormally long or short. This will cause one break in the continuous cyclic variation of capacitances as mentioned above. It has been found, however, that this one break is so y y slight in its effect that it makes no impressio on the hearer, who still gets the impression of continuous pure tone. If it were desirable for' any reason to avoid this interruption, it might be done by omitting the sprocket teeth and holes in the bands, simply using pulleys.

A given band, and each of the stator plates with which it is associated, constitute the two electrodes of one of the condensers l to 9 in Fig. 5. Connection to the bands is conveniently made through the sprockets, which may be of metal. l, The actual schematic circuit for this mechanical arrangement would then necessarily be slightly diil'erent from that of Fig, 1, since one terminal of each condenser, namely the band, would be connected to all similar electrodes (bands) on This rules out the circuit of Fig', l, if the mechanical arrangement of Figs. 10 and -10 be employed. If this mechanical arrangement is to be used in cooperation with the circuit of Figure 1, each group of condensers I-to 3, 4 to B, and I to 9 oiFigure 1 is on a separate belt. as I0, in Figures '10 and 10". The

pulleyslsare constructed with a metallic. rim and insulating web, and the connectionsto Il',

lI i', and i2 arev through a brush riding against,

each rim. This arrangement is not shown in Figures 10 and 10", becausev alternative arrangements may not be shownon a single figure, and

because the addition of a drawing is considered superfluous; in the light of the figures and the written description foregoing, -the construction will be obvious toone skilled in the art. The

plates 33 are the upper plates of I-9 in Figurel,

and are connectedaccording to the diagram there shown.

.Periodic alterations in volume, sometimes called "tremolo, are readily effected by periodically short-circuiting a portion of volume control fil, in Fig'.` 4. This may be done automatically by rotary switch 4|, Fig. 10,;which is on the.

ply a phosphor bronze strip; 1 I'he metallic portion of the switch Il makes connection to volume control Il, Fig. 4, through the shaft on which it is mounted, 'and the bearings of the shaft. The

brush may be directly connected to anotherpoint on control 28. so that when .the brush and rotaty ing portion make electrical contact, that-portion of the volume control which lies between the two points of connection just mentioned, is 'snorted out. This shunting circuit branch`for tremolo `purposes vmaybe similarly connected across a portionuof coupling-element 2 1V in any Vof the- In Figs. 1o and i'o, 1

show means for causing of foot-pedal 39, idler wheel 38 may be raised so as to 'tighten belt 3E. The mass 31 is thus set into to-and-fro motion from the pulley on the shaft of the motor or prime mover 34, through the intermediary of a crank motion. The mass 31 thus periodically' absorbs energy from the shaft of the prime mover and causes it to uctuate in its rotationalvelocity.

In Fig. 10, belt 36, if tightened, rotates crank shaft 31-, thus imparting an oscillatory motion to mass 31 through the intermediary of connecting` rod 31". The mass 31 is constrained to oscillate to and fro in a straight-line path by the guiding influence of bearing 31a In the foregoing specicationI have assumed a single keyboard and set of stops. In more complicated forms of the invention, a plurality of manual or pedal keyboards and sets of stops could be provided, either all within the reach and control of a single musician, or of several. This would make possible, for instance, the simultaneous playing of one part of a composition, perhaps the melody, on one keyboard and with a given tonal quality, and another part, as the accompaniment, in a contrasting tonal quality and on another keyboard. The manner of doing this would be quite similar to the manner in which it is now done on a pipe organ. It is possible, by means of electric circuit'arrangements which I have devised, but which are not described in this specification, to accomplish this using only a single set of bands and stator plates, like the set described above. Various coupling systems, by means of which the tones normally controlled by one keyboard are temporarily made subject to the control of another, or by means of which the depressing of one key is made to simultaneously sound those normally under the control of other keys on the same keyboard, are possible with this invention, just as in the case of the pipe organ. The manner of accomplishing this will be apparent to one skilled in the art of organ building.

I have found that the principle of voltage production by variation of capacitance can be applied in a somewhat diierent manner than that set forth above, and that this modification, and the apparatus for its accomplishment, are particularly useful in non-musical applications. This apparatus I illustrate in Fig. 11b. -In this figure, numeral 20| represents a rotating metallic wheel, whose outer surface is a portion of a cylinder. One edge of this 'surface is bounded by a plane, but the other may be irregular, and of any desired' wavy contour. Connection is made to 23| by means of any suitable brush 205 bearing on the rotating member. In order to continuously vary the capacitance of the condenser, the wheel may be rotatednnidirectlonally by any convenient actuating means, such as shown in Figure 10.

Adjacent to theperiphery of the wheel is a stationary scanning instrumentality, in this case a metallic electrode 202. It is turned edgewise to the wheel, as shown. Measured in the direction ofthe axis of the wheel, thel electrode is somewhat longer than the-width of the wheel,

measured axially; that is, the scanning instrumentality is extended beyond the wavy edge of the wheel.v Due, therefore, to the irregular edge on the wheel, the capacitance between wheel and electrode varies as thewheel rotates. In series be the same function of time as the capacitance between 20| and 202. It is only necessary, then, to cut on the periphery of the wheel any prescribed Wave such as I wish to produce in electrical form, connect the circuit as illustrated, and rotate the wheel at the proper speed. As an aid to obtaining this exact correspondence between the wave on the wheel and the Wave of current or voltage, it is frequently advantageous to shunt a condenser 5| across the variable'one. A circuit fulllling this requirement of exact correspondence I term a distortionless circuit. It is by no means a foregone conclusion that any input circuit whatever will be distortionless in this sense.

The condensers to 9 in Figure 5 are all in parallel with condenser 5I and with one another, insofar as varying currents are concerned. Likewise in Figure IIb, the wheel condenser 20|, 2||2, is in parallel with iixed condenser 5|. In either case, the several parallel condensers may be regarded as having a constant component of capacitance Colin parallel with a variable component C1, the latter being such that its average `value over a long period of time approaches zero as the period of time approaches infinity. For the exact correspondence mentionedabove, that is, for a distortionless circuit, the following conditions must be satisfied: (a) C1 must be small at every instant of time compared with Co, and (b) the reactance of Cu must be small compared with the resistance of l22 for all frequencies within the essential range.

By essential range I mean the following. The varying capacitance Ci is a function of time which, however irregularily it varies; can theoretically be analyzed by Fourier Series or Fourier Integral methods into the sum (or integral) of a large number of periodic functions of time.

For an accurate representation of C1, certain of these functions are essential, and certain of them contribute little to the accuracy. In the term essential range I mean to comprehend vall those frequencies essential to represent C1 with Cn, or if both conditions obtain, then the varying currents in the lcircuitwill be substantially -those which would flow in vwhat I term the equivalent linear circui viz., in a circuit consisting of impedance 22, a. capacitance Co,

y and a source of ,E. M. F., e, in series where and where E' isthe difference. of potential which would exist across the varying condenser if, for the momentits capacitance were held constant at a value Cu. Since E and Co do not vary with time, and since C1 does vary, e varies in strict correspondence with C1. This` E. M. F., e,.then, may be regarded as acting to produce a now of varying current having the same component frequencies as has C1. Since the circuit does not have 'zero reactance, in general, for every one of the component E. M. FIS which caused them,

the current is not in general an Vexact copy of -solved in terms of an equival the capacitance yariation; that is, the circuit is not a` distortionless one. It is only in the case, as above stated, when 22 is a .pure resistance,

-large compared with the reactance of Cn, that distortionless operation occurs. It one oi the two conditionsstated in the rst sentence of this paragraph obtains in .a circuit, that circuit is what I term quast-linear, because it can be v y linear circuit having fixed impedances. In other words, funcwork, is one wherein the elements are so constructed and oi' such yrelative electrical magnitudes that the relationship of the output current or voltage of said circuit to the variable component oi capacitance, or of the reciprocal no! said capacitance, is expressible'with substantial accuracy by means of a linear Adifiierential equation having constant coeiiicients; the derivatives of the equation being expressed with respect to' time.

To make the circuit of Figure 1 quasi-linear, some benefit as regards suppressing musically objectionable harmonics may be had by shunting a condenser across resistor 22 in the manner oi condenser 5I across 22 in Figure 5 and Figure Il". i

lHowever, a condenser in such a location in Figure l is not as eiective as in the two above menc tioned figures, due to the presence oi condensers or 'reslstances I3' to I0' which decouple it materially from condensers l to 0. It .is preferable to increase the ilxed component, Cu, oi capaci- 4tance of each of condensers I to 0 individually relative to the variable component, C1, of each, andso to render the input network quasi-linear with respect to eachV acting individually.

The highfrequency input circuit l0, 22, 20, of Figure 4 may also be quasi-linear. The

condition for quasi-linearity here isr that the Vchange in the impedance of 22, at any of the E. M. F. across 22 which were not present in the capacitance variation, a-result which is usually objectionable, especially in musical applications. Referring to Figure 11h for .illustrati-on, if'A it should prove that a circuit like'that shown was not suillciently linear, one would have three recourses; (a) reduce the impedance 22 external tothe two condensers, or :(b) increase the ilxed shunt capacitance Il, or (c) reduce the magnitude of the capacitance variations Vin 20|,l 202. Any of these measures. will in general also reduce the varying voltage passed on to the ampliiler or other work circuit.l In the interest of linearity, it is generally advisable to avoid approximating a resonance condition in the circuit for' .f an audigi, irequency'in the band to be used, since such resonance will tend to'stress the harmonic having approximately its resonant frequency. j

In thefcircuit of Figure 4, using a high-irequency source it is also sometimes advisable to `avoid marked resonance at any frequency in the neighborhood of that oi the source, for such a' circuit is criticalpandmoreover the curve 'relating capacitance and high-frequency admittance is sharply' curved in the neighborhool of reso- Nation may be adjusted withinv limits by altering tionally defined, a quasi-linear circuit, or netnance, as is well known. This curvature has the -power to cause non-linear distortion. The more nearly linear the curve relating capacitance and root-mean-square high-frequency current, the less the distortion. It is to be understood that the distortionless circuit" is a, particular case of A J`the quasi-linear circuit".

Ii I wish to reproduce in electrical form small waves on thel wheelv which are comparable in tangential dimension with the thickness of the stationary electrode (this thickness also to be measured in a tangential direction) it may be desirable to place around electrode 202 a shield or guard 200. This shield is insulated 5 from electrode 202 by means of air spacing or of the insulating solid material 204.V It is to be noted that the insulating material 20I is so disposed that it is substantially free from shifting electrostatic ilux, the iiux in 20| having been virtually iixed by the guard. 'I'he shield is connected to one or the otherend of the battery 2l.

as shown, and hence serves to confine the electrostatic field quite closely to the addacent faces of wheel and electrode. The principle is quite like that oi the guard-ring'n used in certain laboratory measurements of electrostatic capacitance o! cables, and the like. This principle is here ii- A lustrated in connection with the irregularly shaped wheel. It is to be understood, however. that it Ahas application to means as herein described for producing sinusoidal or other periodic waves such as the means illustratedin Fig. l0. Its mode of application to these will be apparent by analogy with its use in Figure '11".

The varying voltage produced by this device Y can be used in a variety of ways which will be apparent to one skilled in the art. It may. for example, be applied to an amplifier as are the alternating voltages in the foregoing ilgures.

VRather than being cutfinto the periphery of a wheel, the irregular edge which causes alterations in capacitance may in certain forms of the device be cut into a belt or tape of metal. This tape may be'endless, or not, according to the use to which it is to be put. It is evident that the wave of voltage or current produced need not be periodic, for a"given point on the wheel, tape, or 'belt need pass the electrode only once. In this form, then, the invention is not necessarily a 'meansoi' producing periodic o'r alternating currents and voltages, but may produce currents and voltages varying in a very complex manner indeed. Nevertheless, it will not .be diiiicult to determine how to cutv the irregular edge to arrive at 5 a given desired law oi current and voltage variation, for therelmay be exact correspondence between the shape of the edge and the shape oi electrical change resultant.

- Another actuating vmeans for continuously common in musical lapplications. Ii' this latter'V member be given impulses by electrical or mechani'cal means, at intervals whichare not too great, itwill be kept in continuous vibration at its own'natural frequency or frequencies. Its

amplitude will, of course, die out slightly between impulses, but withr proper arrangementsf-its motion may be regarded for all practical purposes as periodic. The amplitude of capacitance varithe direct exciting E. M. F.s, and by means of series impedances, as above described.

The above paragraph describes vjbratiie means for originating complex waveforms directly, without resort to electrical synthesis of tonal partials. In such devices in their simplest form,

the electrodes are not shaped in accordance with the waveform, and the variations of capacitxr occur by virtue of variations, in response to vibration, of the effective thickness of the airgap intervening between the electrodes. In a variant of the vibratile type of condenser, described below, one or more of the electrodes is shaped in accordance with the prescribed waveform, and

-the waveform maybe substantially sinusoidal, as

will appear. The electrode shapes may be arrived at empirically or, in the construction of Fig. 12,

`they may be calculated, provided the relative electrode displacement is substantially sinusoidal, and the airgap remains substantially constant, as-

will be evident to one skilled in the art. The construction to be described will be such that each condenser, by itself, will originate a substantially sinusoidal waveform of capacitance. t

It will be also evident that such a vibratile condenser can be used for each of the condensers diagrammatically illustrated at I to 9 of Figs. l and 5. In such a case, each such condenser will originate an individual tonal partial. Preferably, each vibratile member will describe an approximately simply harmonic motion, and there will be one for each partial tone of each pitch which it is intended to produce.

Parts B0 to 83, inclusive, of Figure l2 constitute a condenser as illustrated diagrammatically at I in Figure 6b. Parts 8U and 8l constitute a free reed, similar to that in the reed organ, and arranged to be vibrated pneumatically, as in the reed organ. Part 80 is the frame of the reed, and 8l is a strongly resonant vibratile tongue.

' The end of the tongue BI may be bent to form the electrode B2, or 82 may be a separate piece associated with the tongue BI by means of solder, rivets, or any suitable linkage whereby the vibrations of the tongue are communicated to the movable part 82. Part 83 is a fixed electrode distinct from 82, suitably insulated therefrom, and separated from it by a thin airgap. Figure 12 shows the two electrodes, 82 and 83, as being substantially coaxial cylindrical segments, the axis of the cylinders being near the line oi at-l tachment of parts 80 and 8l, so that the electrode l2, for all practical purposes, oscillates about this line. Under these conditions, the two electrodes remain at a substantially nxed distance from each other during vibration, and the thickness of the ai'rgap remains vfixed for all practical pur- It is evident that, during vibration, the effective area.. of the two is a linear function of their displacement relative to each other under these conditions. Likewise, the capacitance between them, being directly proportional to their effective area, is a linear function of this displacement. Hence the capacitance is a substanv tlally sinusoidal function of time, being necessarily a "c0py of the intended substantially sinusoidal'partial waveform, under the construction herein illustrated and described.

Attached to the part 82 and insulated therefrom by the insulation 8l is the guai-.d electrode 85. The guard electrode 85 is connected through the wire 86 to one terminal of the source '2 I. Attached to the fixed electrode 8l and insulated therefrom by the insulation B1 is the guard electrode 88. The guard electrode 8l is connected by the wire 89 to one terminal of the source 2I. Parts 24 and 25 of Figure 12 are respectively an amplifier and a sound translating device. The

remaining reference numerals of Figure 12 designate the same circuit elements as do those of Figurekb, and these elements operate in the same manner. i

' The vibratile members may be set in vibration by mechanical means such as single or repeated strokes with hammers or bowing as inv the violin. 0r by means o'f magnetic impulses, in which case the members would have to be ferromagnetic material or else carry an electric current, in a magnetic iield so that the necessary electromagnetic reactions could be brought to bear on them or else be attached to such elements. An inexpensive and simple means of impulsing them is to fix, adjacent to the vibratile members, stationary electrodes in addition to those mentioned above.` A periodic potential difference applied between' these and thevibratile members will set up electrostatic forces suiiicient to set them into vibration, damped or undamped. A

Condensers I to 9 and others whose capacitances are caused to vary by mechanical means. may have a xed element, plate or electrode and a movable element, plate or electrode caused to move relative to the fixed member by a movement of translation, reciprocation or rotation. through the agency of a motor or any other actuating means.

Since the capacitance oi' a condenser may be varied by altering the distance between its electrodes as well as by varying their dimensions, the working surfaces Iof the electrodes need not be portions of planes or of cylinders, but may be so formed or configured that as they move in relation to each other, their active portions approach or recede from each other. They might therefore be corrugated in form, for instance. The capacitance of a condenser is also a function of the dielectric between its electrodes. Hence the dielectric may be of variable width or thickness or dielectric constant from point to point, and` it may move relative to one or both of its associated electrodes. All of these variants are comprehended withinthe scope of my invention.

The shapes of parts, especially airgaps, dielectric, and electrodes in the condensers of my Figures 10 and 11b are naturally very important. because variations therein will alter the waveform originated by any condenser of such construction.

Such parts must thus be specially and appropriately shaped for the particular waveform prescribed, as is taught elsewhere herein. Such shaping maybe arrived at by empirical methods. or by precalculation, or by a combination of these methods, as seems most appropriate, without departing from the spirit of my invention. None of the claims is limited to any particular method of' er capacitance can be calculated by the wellknown formula for a parallel plate condenser. This formula shows that the capacitance is directly proportional to the product of the area of the dielectric, the dielectric constant, and the reciprocal of the separation between plates. If

l the plates or the lines of force are not strictly parallel, or if the dielectric is non-homogeneous "f (as when it is composed partly of air and. partly of a solid), some correction must be made. That is, an effective area, an effective dielectric constant, or an eifective separation should be used in the formula. Only in an ideal case are effecv tive and actual values equal. The same principles of calculation apply, regardless of which of these three en'ective quantities is or are varied. Regardless of whether the effective value of one of these quantities is or is not exactly equal u to the actual value, it may still be considered that such an effective value can be arrived at either by calculationor by experiment, and that for capacitance. y

` In' all condensers embraced by my invention, there is an actuating means, such as the wheel of'Figure 11b, or the belt of Figure l0, to which a part of the condenser is attached, and by which that part is made to move, with resultant variation Aci! one of the three effective quantitiesv 'mentionedg above, or else the means and part are identical. Ihere isa cause-result relationship between the displacement of an actuating part and each of the variable quantities. This relationship is expressible by a diii'erential equation. as is well known. If this equation is other 1 than a linear one with constant coelcients, the

effective quantity issaid to be a non-linear function of the displacement of the actuating means, and conversely. a linear equation with constant .coefficients bespeaks a linear function of the y displacement. V

In the ,interest of easy design of a condenser like those of Figures '1'0 and 1lb, it is very advantageous to makeA the effective width (dimen- 20! for each v Y ity of condensers like that of Fig. 11h but having `a sinusoidally shaped electrode 2li, may be used in the circuit locations of any of the condensers I to 8 in Figures 1 and 5 or of I in Figure 6*. The rotary form of condenser obviously is applicable to a musical instrument.

I'his invention is not limited to the production' of periodic voltages and currents; nor is it limited to the production, in separate and distinct parts, of a plurality of sinusoidal alterations with subsequent synthesis of these in an electric circuit. For it is evident that the variation of capacitance may follow a certain law ,as` a function of time for a limited period and'then, be fore this variation has begunV to4 repeat itself.

the moving part of the apparatus may be stopped Except in very limited instances, however, I preits use in the formula will give the correct value sion inthe direction of relative plate motion) v narrow compared with a haltwavelength on the wavy edge, for in such case the edge need merely have the shape of the desired function which the waveform of capacitance is to follow, To this end, 'it is often necessary to control the' fringing by shield or guard electrodes as above contem. a0

dielectric between themare regarded as belonginstant-to-instant proportionality is n t neces'- sarily present.

of the details of my invention are applicable to other forms oi' the parts with which ,they are associated. For example, a. plurality4 of wheels. onefor each fundamental, may carry iin-,like electrodes `similar to electrodes Il on the belts 'ci P18. 10. Asa second example, a pluralthat separate polarizing or exciting sources may be used for the several condensers.

Where a claim includes selectors "means `for selecting," or the like, I mean to include couplers, stops, keys, or similar instrumentalities, except as further limited bythe language of the claim. A

In those claims which include means for Droducing variations of current, voltage,` electromptive force or potential, or means for varying 4'a capacitance, current, electromotive force, or potential or which include similarly worded phrases, I mean to cover frequencies or waveforms corresponding to diiferent notes of any musical scale or system of tempelamentaovertones or other frequencies, or waveforms, periodic or non-periodic, musical or non-musical, except wherethe claims-are limited by their terminology, and two or more of these of like or unlike fr cies or waveforms may be combined by selectorsas above dened.

As is well known in the electrical art, a c ou- Y Where the claims refer to a. condenser, the word is used in accordance with vthe following o deiinition. Electrodes so remote from one another, or so situated relative to one another, that there-can be nouseful electrostatic flux in the ing to separate condensers. Conversely, electrodes so close together, orso situated relatively, that there may,l be useful ilux between them are parts of the same condenser.- Thus, in Figure 10 are illustrated twelve electrodes, 33. These have no useful vilux between them at anyv time, and Y electrode 3i, temporarily two eiectrodes^therefore denser'for the time.

' electrode 3| has progressed to another stationary given stationary electrode Il and that particularelectrode Il, then it and thatoother ctn'istituteV a second condenser. Hence Figure 10 shows twelve separate condensers, while Figures 11b and 12 each illustrate one condenser.

When I speak in the claims of ,condensers, I mean a. plurality ofthe individual condensers as above defined. y

Where I use thephrase, substantially sinusoidal Waveform or the like, I mean a waveform` which `is nearly enough sinusoidal for the pur" pose at hand.- I do not mean to include in the phrase all manner of periodic waveforms By a partial tone or a partial I mean to imply a substantially sinusoidal waveform intended to be used as one of the components of a complex periodic waveform. By a complex periodic waveform in the specification and claims, I mean to include all periodic waveforms not comprehended under the above definition of a substantially sinusoidal waveform.

`Where I refer to a part of a condenser or the like as being shaped in accordance with" a waveform, or shaped in a manner appropriate toy a waveform or where I use similar terminology, I do not of course mean to imply that any part of said condenser, or the like, is necessarily a photographic image of the Waveform, but only that it is of such a shape that said waveform will result from the operation ofthe condenser in the manner described, and that the shape is one of the factors responsible for the waveform.

Where I referto an electrode or to electrodes, I mean to include in this term only bodies, surfaces, and areas sufficiently conductive so that each of their active portions behave,

for the purposes of this application, as equipotential surfaces. Bodies, surfaces, and areas such as an emulsion of silver, are not included, since they would not behave as equipotential surfaces to afdegree suitable for present purposes.

In musical applications, the phase relationships between partials of a complex tone is not important, as shown by D vC. Miller, The Science of Musical Sounds, page 62, published by the MacMillan Co., 1926. In Figure 10, the placing of the scanned electrodes will, of course, determine the phase relationships between the fundamental and its harmonics in the wave originated.

In Figure 11b, it is implicit in the shapes o-f the electrodes. As this relation is not important musically, exact spatial relationship of the electrodes is also not important in suchV applications, and no particular relationship has been disclosed in Figure 10. Thus, the use of the word, "prescribed-waveform does not necessarily carry an implication as to definite phase relationships.

Where the claims recite a coupling element, coupling device, or coupling impedance, I mean to include thereby any suitable element comprising a substantial amount of impedance. Such an element may be made up of resistors, capacitors, inductors, or transformers, singly or combined in any manner suitable for coupling purposes. Simply wires, leads, or buses having no appreciable impedance are not suitable couplers becauseof their lack of impedance, and

are4 not included in the phrase.

In` the claims, where I refer to continuously varying, continuous variation," fcontinuously moving, or the like, I mean to imply that the motion or variation is not startediand stopped by selectors inthe act of'selecting tones, timbres, sounds, condensers, or sources, but that it continues in any actuating part, source, or .condenser when the device as a Awhole is in use,

independently of whether that particular part,

source, or condenser is in use for voltage production or not and that selection, if any, is effected by establishing electric connections to a source, or condenser.

Except when further limited, as by they/'ord conductively or the like, where the claims speciiify means for establishing electric circuit connections or include similar phrases, I do not mean to be limited to devices which make electrical contacts such as a switch. Such devices may bring electrical parts into inductive relationship as in part 65-11 or may be otherwise inductive, and the electrical influence through such selectors may be via a solid or fluid path.

No claim is made herein to any element in the field circuit of an alternator, or the lamp-exciting circuit of a photoelectric device.

In the claims in which I use the term network or circuit, I mean to cover all conductors, or electrical networks, however complex, (except where limiting words such as series are included) in which there can be an appreciable transfer of electric charges by metallic, galvanic, ionic, or electronic conduction; I mean to cover also such instrumentalities as condensers, transformers, and gaseous vacuum,I and photoelectric tubes, in which the airgaps are so short as to connect the adjacent parts through electrostatic or magnetic induction. The terms are to distinguish from airgaps through which only an infinitesimal portion of the current can be transmitted and from those in which energy transfer occursl cliiefiy by electromagnetic radiation, asin wireless transmission.

Whenever, in the claims, I refer Vto a source of polarizing or exciting electromotive force, or

the like, unless further limited, I mean to specify a source whose internal impedance and electromotive force are either substantially invariable, or else vary periodically at a rate above or below audibility. The current in such a source may. however, vary a-t an audible rate in response to the variations in impedance of the external circuit connected to it.

In these claims, where reference is made to an linstrument for producing alternating electric currents and voltages or where some similar phrase is employed, it is not to be inferred that the production of alternating electric .currents and voltages is the ultimate purpose of the instrument referred' t0. The ultimate purpose may, for example, be the production of musical sounds.

In the claims, where a part is described as moving relative to another part, itis to be understood that either or both of the parts referred 'to may be in motion relative to other portions of the device such, for example, as its supporting base -or framework. Relative motion between the two parts is the essential feature.

The drawings and description illustrate and describe what I now consider to be preferred forms of the `device for production of musical tones or of alternating currents or electromotive forces, by way of illustration only, while the broad principle of the invention will be defined Aby the appended claims. f

What I claim is:

l. A device for originating a prescribed wav'. form, comprising a. quasi-linear circuit, a condenser of variable capacitance in said circuit for varying the negative reactance therein and actuating means for continuously varying the capacil tance of said condenser in accordance with said 2. A device for originating waveforms translatable into sound, including means for producing ,audio-frequency electric currents by mechanical motion between parts thereof, actuating 'l means for maintaining said motion, andan electricai network having output terminals and a shunt branch and being fed by said ilrst means; said branch having a negative reactance and being adapted for by-passing audio-frequency components of current and for thereby reducing the magnitude of musically objectionable harmonic currents setup by said first means across said terminals.

3.k A device for originating a prescribed waveform, comprising an input network, a portionpof which network has a capacitance which varies as a. function of time; said capacitance characterized by the fact that itsvariations are small compared with its fixed component of capacitance, whereby quasi-linearity is obtained.

4. A device for originating a prescribed waveform, comprising an electric circuit, a condenser of variable capacitance in said circuit for varying the negative reactance Itherein, and vactuating means for continuously varying the capacitance sources' whose hereinbefore mentioned terminals are connected to separate selectors being connected at their other terminals to a common conductor; said network comprising, upon closure of selectors therein, a plurality of circuit meshes, each of which meshes contains one of said sources; at least a part of said coupling element,

and one of said impedance elements; the impedadapted to set up arr electrostatic field aroun and between them, parts of said condenser adapt ed to have relative motion, and 'a guard electrode .for modifying said eld.

oi said condenser in accordance with said wavel form, and a ilxed condenser in said circuit for rendering said circuit quasi-linear.

5. A device for originating a prescribed waveform, comprising an input network, means for producing audio-frequency electric currents -by 9.V A variable condenser, comprising an electrode, a guard electrode, and a strongly resonant vibratilemember distinct therefrom for varying -the capacitance of said condenser.

10. A device for originating a prescribed wave-v form, comprising parts having continuous relative' motion between them, driving means for obtaining saidmotionsand means for superimposing upon said motion an additional component oi motion at a slow periodic rate, whereby vibrato Aeil'ects areproducible.

mechanical motion between parts thereof. actuating means for maintaining said motion, an amplifier, and aicoupling device for coupling said network and ampliflerisaid network having a branch or negative reactance shunting said coupling device. wherebyl relatively high audio-frequency components oi' current in said coupling device which are musically objectionable may be reduced.

6. A device for originating waveforms of electric current translatable into sound, comprising an input network. a plurality of sources of such current, actuating means for producing relative rotation between parts of'said sources, an amplifier having input terminals, a coupling element coupling said network and said terminals, and a. plurality of circuit branches in said network -'conductively connecting one terminal of each of said sources to said coupling velement and adapted to conduct said translatablel current between said terminal and said coupling element,

each oi.' said branches including in series an impedance element and one pair or terminals of a multipole selector, and the impedance of each oi' said impedance elements being sufficiently great an input network, a plurality of sources of such current, actuating means for producing relative rotation between parts of said sources, an amplifier having input terminals, a coupling element l coupling said network and said terminals, and a I pluiity of circuit branches ins'aid network conduc vely connecting one terminal of each of saidl sources to said couplingelement and adapted to conduct said translatabler current between said terminalJ and said-element, each of said branches including in series an impedance element and.4 one -pair of terminals of a multipoleselector;

11.l A device for originating a waveform of electric current, comprising paris` having continuous relative motion between them, driving means for obtaining said motion, and means which include a periodically varying mechanical impedance for superimposing upon said motion an additional component of motion'ata subaudible frequency, whereby vibrato .effects are producible. 1

l2. A device for originating waveforms which comprises an electrical network and a tremolo actuating means; said network including aninput portion and a vacuum-tube system receiving from 13. A device for originating waveforms, includinga tremolo-actuating means and an electrical network; saidnetwork comprising an input portion, a vacuum-tube system, and a coupling element coupling said portion and the input terminals of said system; said portion including means for producing audio-frequency variations of current therein and a circuit branch shunting at least a portion of said element and external to said means, whose impedance is varied by said actuating means; the voltage fed to said terminals by said portion being modulated by the variations of said impedanceat a subaudible frequency, whereby tremolo eil'ects are the output of said system.

14. A device for originatingwaveiorms. comprising an electrical network and sources in said network `for producing audio-frequency variay tions of current therein; said network containing apair, of electrical contacts alternately opened and closed at a slow periodic rate for the production of tremolo eiiects upon the variations of c urrent from a plurality of said sources, said contacts when open having impressed across them by said sources a variable potential translatable rinto Sound.

15. A device for originating a waveformcomprising an electrical network, and means for proproduced in ducing in said network audio-frequency variations of current; in said network a coupling element and a tremolo circuit branch external to said means having an impedance which varies at a slow periodic rate, and shunted across at least a portion ofsaid coupling element,

16. A device for originating waveforms translatable into sound, comprising a plurality of condensers, actuating means for varying the capac-s itances of said condensers in accordance withsaid waveforms, a source of electromotive force for polarizing said'condensers, and timbre control means adapted to control the polarizing potentials applied to said condensers by said source; said timbre control means comprising a plurality of timbre selectors, a plurality of buses each individual to a given partial and common to that partial at a plurality of pitches in a musical scale, and a plurality of impedance elements individual to each of said buses for determining the polarizing potential on each of said buses.

17. A device for originating waveforms comprising a plurality of sources of varying electric currents translatable into sound, a coupling element, a plurality of selectors, means actuated by said selectors and adapted to complete circuit connections for conveying said varying currents between said sources and said element, and means actuated by each of said selectors for preventing musically objectionable current crnponents in said element by short-circuiting a current path joining one of said sources and said element when it is desired that that source shall produce no current in said element by that path.

18. A device for originating a waveform, cornprising a vacuum-tube system, an input circuit adapted to be connected to the input terminals of said system, a condenser of variable capacitance adapted to vary the negative reactance in said circuit and to thereby produce across said terminals a voltage translatable into sound, actuating means for continuously varying the capacitance of said condenser in accordance with said waveform, an impedance element, and electrical means in said circuit for gradually inserting said element into said circuit and for thereby gradually varying the eiiect of said condenser upon said circuit and vsaid system in a manner' substantially free from musically olijectionable transients.

19. A device for originating a waveform translatable into sound, comprising an electric circuit, means for producing current variationsin said circuit, electrical selectors for selecting said means, and means for sustaining said sound by controlling the rate of variation of an impedance in said circuit externalto said first means after said 'selectors have ceased to move.

20. A device for originating waveforms Aof varying electric current translatable into sound. comprising a vacuum-tube system, a plurality or electrostatic condensers whose' capacitances vary at the frequencies of a musical scale for producing current variations in said vacuum-tube system, mechanical means for continuously varying said capacitances, electrical selectors, circuit' branches selectively closable by said selectors between terminals of said condensers and terminals of said system, and adapted to convey said translatable current between terminals of said condensers and said system, a sound translating device excited by 4 said system, variable irnpedance means for rendering gradual vthe onset or tones when said selectors are operated, and

and to correspondingly control the time interval ing varying potentials at selected tone frequencies, electrostatic means for determining the manner in which said varying potential varies for producing tones of various timbres, a sound producing circuit, meansfor impressing potentials at selected tone frequencies derived from said rotatably driven means and of selected tone timbres derived from said timbre determining means upony said sound producing circuit,

and means for prolonging the duration of the tones emitted by said sound producer..

23. n a system for the production oi music, a multiplicity of continuously varying capacitative reactance or" differing characteristics, means for simultaneously operating said varying capacitative reactances for producing diiierent tone pitches, an electron tube system having input and output circuits, a sound producer connected with said output circuit, a plurality or tone pitch selectors, a variable impedance adapted to be varied by each of said selectors for ren dering selected capacitative reactances effective with respect to said electron tube system for correspondingly controlling the operation of said sound producer, and means adapted to control and inhibit the variation of said impedances during which one or more of said capacitative reactances remain effective with respect to said electron tube system.

24. In a. system for electrically producing sound, an electromagnetic sound producer, an electrical circuit for controlling the electromagnetic sound producer, a multiplicity of continuously varying capacitive reactances for controlling the operation of said circuit, a plurality of tone selectors, in said circuit a plurality of circuit branches each selectively closable by one of said selectors, and means adapted to` control and inhibit the reopening of said branches and to correspondingly prolong the time period over which one or more of said continuously varying capacitive reactances control said circuit.

25; An electrical musical instrument for originating prescribed waveforms translatable into ,adapted to be energized from said condensers and to -translate said waveforms into sound, a plurahty of keys, selecting means actuated by said keys for sustaining said sound at gradually diminishing volume, and a speed control member other than said keys and said means for regun lating, during performance on said instrument, the motion of said selecting means and the rate of diminution of said volume.

26. In an electrical musical instrument: an input network; 'a sound translating network; in said input network, a condenser of variable capacitance; a tone selector adapted to impose the eect of said condenser upon said network; actuating means for continuously varying the ca- Vtorni of current translatable into a musical tone; in said'condenser, a pair of electrodes maintained in relative motion lby said means in said input network, a coupling impedance adapted to couple together said input network and said translating network, a source of polarizing lpotential for said condenser, and circuit elements connecting together said pair of electrodes, said impedance; and said source in series.

'put network; in said network, a condenser of variable capacitance' for originating a varying polating network adapted to be energized by said potential; a source oi potential of supersonic frequency for polarizing said condenser; and means connectible between said input and translating networks for demodulating said potential.

28 In an electrical musical instrument: a vaci uumtube system; an input network adapted to be connected to the input terminals cf said sys--A vtem;.a source oi' variable electromotive force translatable' into sound; means for continuously.

actuating said source; a tone selector for said source; and a variable resistor in said network and controlled. by said selector for gradually varying the effect of said source upon said network and said system. l e

29; In a device for originating a prescribed waveform: an electrical network; means electri-2 cally connected in said network for producing current 'variations therein'; and electrical mans for selecting said rst meansand for gradually 1.0 27. In an electrical musical instrument: an in-y pacitance of said condenser to originate a wavehavlng two terminals; a plurality of selectors for said condensers; actuating means for continuously varying the capacitances oi' said condensers in accordance with said waveforms; a source oi Ipolarizing electromotive force for said condensers; a coupling impedance having a plurality of terminals; circuit elements connecting said source with a terminal of saidimpedance and a terminal of each of said condensers; and a plurality of circuit branches selectively closable by said selectors-between a terminal of said impedance and a terminal of one of said condensers, lthe terminals connected to said branches being other than those connected to said source.

33. In an electrical musical instrument: an

electrical network; in said network, a plurality of generators of electric currents translatable -by saidnetwork into musical tones at a plurality of frequencies in a musical scale, each of said generators being of the type in which the amplitude of its translatable current may be con-v trolled by the value of an exciting potential irn-l pressed -upon it; in said network, a source of exciting potential i'or said generators; and, connected in said network intermediate said source and said generators, the combination of a plurality of circuit branches, a plurality of electrical conductors, and a group oi current-limiting impedance elements individual to each of said convarying its eilect upon said network, said felec- 'tricalmeans comprising a pair of electric .con-

tactil.v a condenser oi' variable capacitance, and a common mechanism for operating said contacts and for varying said capacitance.

30. In an electrical musical instrument: an electrical network; in said network, a'plurality o! .generators of electric currents translatable byY said network into musical tones at a plurality of frequencies ina musical scale; and, in said network, the combination or a plurality oi' circuit branches, a plurality oi electrical conductors, and

i a plurality of current-limiting impedance .ele-

ments individual to each of said conductors and adapted to beconnected thereto; each o! sai'd conductors together. with its associated imped# ance elements `being connected during operation Vlo1' said instrument `through certain oi said ductors; each said group of impedance elements being connected between their associated conductor and terminals of said source to determine themagnitude of exciting potential applied to their associated conductor; and each of said conductors being connected duringoperation .of said `instrument through certain of said branches to generators which supply a given tonal'componentI at a pluralityA of said frequencies and .being adapted t determine the strength of said component at a plurality or said frequencies. si-

multaneously. f

34. In an electrical musical instrument: an

velectrical network; .in said network, a plurality of condensers, and a source of polarizing potential for said condensers; Vactuating means for varying the capacitancesof said condensers in laccordance with tones of a musical scale: a plurality of means for selecting said condensers and for imposing their combined eects upon said network, each of' said means :or selecting comprising a plurality of pairs.of switch contacts, a common control member vfor simultaneously closing-said contacts and, in sexies witheach pair,V

a terminal and a voltage dividing resistor; eachof said resistors and pairs being individual to its respective control member; said terminalsveach f being connectible'to said source'. through a pluar plurality of said frequencies and being adapted' to .determine "the strength oi' said eomponentat a` plurality .of Vsaid frequencies simultaneously;4 3l. In an electrical-musical instrument: an

" electricalnetwork; in said network, aplurality rality of current paths, each pathy comprising one of said resistors and one or said pairs: the plu` rallty of'pairs through which a given terminalv is 1 connected being-controlled by separate control members; thepolarizing connections for saidconor generators oi' .electric currents translatable by l saidnetwork ainto' music'altones at a plurality of frequencies in a..musica`l scale; a plurality oi timbre seiectorst'and. in said network, a plurality offcurrent-litniting impedance elements each individual lto one of said selec'torsand` seA leotively oonnectible' by said. selector rto other portions'oi said network to determine'the strength oiga.` g'ivencomponent oi a musical-tone at a pluralitiiii said Vfrequencies simultaneously. v

, In a device tororiginatlngwayeformsetrans-I' latable intosound; a plurality-oi' condensers eich,A

densers yeach being made to-one ofthe vai'ore` mentioned terminals and t@ s point on said source; the Y potential or each of said rterminals being determined bythe operationof said controlA members; said plura'iityof means comprising a plurality. of

s additional current connectingone of said terminals with av common terminal of said source, each o! said' last-named paths comprising not being adapted for closure by any o! the control-members; .said pairs, terminals, and resistors beinggincluded in said network.

whs. esca a voltagefdividing resistor, and f 

